I have a 99 tj with a 3 speed automatic and just wondering if it has an overdrive, at about 30 mph it shifts into drive, and at about 40 mph it shifts again and drops the rpms down. I don't think it has a overdrive but cofused what the shift is at 40.

There is no overdrive in a 3-speed auto. However all modern Jeep automatics utilize a locking torque converter. When it locks it will indeed drop a few engine RPMs - the same amount as the converter slippage at that speed. Once locked, the exact 3rd gear ratio is in use, which in the case of the 3-speed TJ transmission is 1:1, but not overdrive. You are not the first to mistake this for another gear - and many Jeep owners never seem to notice this at all.

There is no overdrive in a 3-speed auto. However all modern Jeep automatics utilize a locking torque converter. When it locks it will indeed drop a few engine RPMs - the same amount as the converter slippage at that speed. Once locked, the exact 3rd gear ratio is in use, which in the case of the 3-speed TJ transmission is 1:1, but not overdrive. You are not the first to mistake this for another gear - and many Jeep owners never seem to notice this at all.

I noticed it day one in ours...but I DEFINITELY think there still needs to be another gear, PLUS the lockup...

Damn, I just found this old thread and had been scratching my head for some time now... I have "counted" 4 gears over and over when I get my TJ up to highway speed and could have sworn it had a 4th or OD gear. Duh do I feel kinda dumb now. But this shows what a search will turn up.

I'm sure that 30 years later, I still have friends that would swear in court my old Triumph TR-6 British-made 2-seat sportscar had an 8-speed manual transmission. It didn't of course but I could sure fool them into thinking it did with its electrically controlled 2-speed rear axle. To this day I don't know how that 2-speed rear axle worked but it was fun fooling my friends into thinking my TR-6 (kind of like an MG) had an 8 speed transmission by secretly shifting the axle back and forth via a turn-signal like lever on the steering column between High and Low as I shifted the 4-speed trannie.

Just goes to show that trannies and how many speeds they really have can fool the best of us.